The present invention relates to a control circuit for an ink jet head in which the drops of ink are expelled from a nozzle of a conduit filled with ink, in response to a control signal, said ink forming in said nozzle a meniscus having a natural resonance frequency.
As is known, by exciting the transducer with a voltage pulse, a pressure wave is generated in the conduit, which expels a drop of ink which is repeatedly reflected at the end sections of the conduit and causes oscillation of the meniscus at its resonance frequency. Such oscillations substantially interfere with the subsequent emissions of drops and reduce the frequency of drop emissions.
A method has been proposed for reducing the effects of reflection of the pressure wave and the oscillations of the meniscus, which comprises connecting the print element to the ink container by means of a tube of flexible material. Since the tube is normally some tens of centimeters in length, that means that the arrangement occupies a substantial amount of space, giving rise to bulky print devices of substantial weight, more particularly when the head uses a large number of tubular elements.
Likewise, a control and cancellation circuit for eliminating the reflected waves in a print element has also been proposed, in which the piezoelectric transducer is excited with a voltage wave which is without harmonics. Such a voltage wave, of predetermined duration, excites the transducer to eliminate the reflected waves by superimposition. However, while there is no reflection of the pressure wave in the ink conduit, disturbances may be found in the emission of a drop of ink, caused by parasitic vibration of the ink meniscus in the nozzle at the moment at which the drop becomes detached from the nozzle.